The comparisons of position players across the ages is much simpler than it is for Pitchers for one simple reason. The changes to the game have not affected much the number of times that a player comes to the plate. 600 at-bats in a season and 9000 at-bats in a very good long career have been standards that batters can reasonably achieve throughout time. Pitchers' workload has changed dramatically over the ages. 320-340 innings would be perfectly reasonable seasonal totals for a starter in the years 1910-1920 or 1960-1970, whereas 220-240 innings would be a good total for a current starter.
Without further ado, here's the chart. The figures reflect the performance of the average of the 3rd-5th best starter in each category (except for home runs, which reflect the 3rd-5th highest figures.) The bracketed figures in the K/9, W/9 and HR categories are league average K/G, W/G and HR/G. DER stands for defensive efficiency rating and reflects the percentage of balls in play turned into outs (680 means that the defence turned 68 per cent of balls in play into outs). The basic data has been obtained from baseballreference.com.
Year League IP K/9(Lg.) W/9(Lg.) HR(Lg.) ERA+ DER 2005 NL 236 8.7(6.7) 1.7(3.3) 34(1.0) 151 693 AL 227 8.1(6.1) 1.2(3.0) 32(1.1) 135 695 2000 NL 243 8.7(6.7) 1.8(3.8) 34(1.2) 154 689 AL 225 8.4(6.2) 1.9(3.7) 33(1.2) 136 684 1996 NL 237 9.1(6.7) 1.7(3.3) 29(1.0) 146 687 AL 246 7.9(6.2) 2.4(3.8) 35(1.2) 142 682 1990 NL 233 8.4(5.7) 2.0(3.2) 22(0.8) 143 701 AL 237 8.1(5.6) 2.1(3.4) 26(0.8) 140 699 1985 NL 270 8.0(5.5) 1.5(3.3) 26(0.7) 160 707 AL 262 6.7(5.2) 2.1(3.3) 30(1.0) 141 704 1980 NL 263 6.9(5.1) 1.9(3.1) 23(0.6) 126 700 AL 276 6.4(4.6) 2.0(3.2) 28(0.8) 138 698 1975 NL 278 7.2(5.0) 2.1(3.5) 24(0.6) 139 701 AL 300 7.3(4.9) 2.2(3.5) 28(0.8) 135 703 1970 NL 291 7.8(5.9) 1.9(3.6) 30(0.9) 133 697 AL 291 7.7(5.6) 2.2(3.5) 32(0.9) 131 711 1965 NL 297 8.3(5.9) 1.6(2.9) 27(0.8) 148 704 AL 265 7.9(5.9) 1.8(3.3) 28(0.8) 134 715 (154 game schedule) 1960 NL 272 7.5(5.5) 1.6(3.2) 27(0.8) 132 704 AL 255 5.9(4.9) 2.0(3.6) 26(0.9) 121 712 1955 NL 241 6.0(4.4) 2.2(3.4) 30(1.0) 121 714 AL 239 6.0(4.4) 2.7(3.9) 22(0.8) 142 710 1950 NL 282 5.7(4.1) 2.3(3.7) 31(0.9) 136 707 AL 255 5.3(3.7) 3.0(4.4) 25(0.8) 131 700 1945 NL 241 4.8(3.1) 1.8(3.4) 15(0.5) 142 702 AL 255 4.5(3.4) 2.2(3.4) 12(0.4) 145 708 1940 NL 281 4.5(3.5) 1.8(3.1) 18(0.6) 133 701 AL 270 5.5(3.8) 2.4(3.6) 21(0.7) 141 691 1935 NL 270 4.8(3.8) 1.6(2.7) 19(0.5) 134 686 AL 276 4.8(3.2) 2.3(3.7) 17(0.5) 136 688 1930 NL 261 4.7(3.1) 1.9(3.0) 24(0.7) 123 668 AL 289 5.6(3.3) 2.0(3.2) 19(0.6) 132 679 1925 NL 274 3.8(2.8) 1.7(2.8) 18(0.5) 134 675 AL 259 3.7(2.7) 2.2(3.5) 15(0.4) 139 679 1920 NL 302 4.1(3.0) 1.5(2.4) 9 (0.2) 135 693 AL 310 3.9(2.9) 2.2(3.1) 13(0.3) 139 680 1915 NL 297 5.3(3.8) 1.5(2.6) 8 (0.2) 129 704 AL 305 5.4(3.9) 1.8(3.4) 6 (0.1) 153 695 1910 NL 304 5.2(3.6) 1.9(3.2) 7 (0.2) 142 689 AL 315 6.1(4.2) 1.7(2.8) 7 (0.2) 167 693 1905 NL 337 5.1(3.6) 1.8(2.6) 7 (0.2) 140 685 AL 329 5.5(4.1) 1.8(2.4) 7 (0.1) 139 708
If you look carefully in the statistics, you'll see Babe Ruth in the American League in 1920 and Rogers Hornsby in the National in 1925. You'll see the hitter's paradise of 1930, and the sloppy baseball of wartime. You can see differing strike zone patterns in each league for a decade or more.
We will come back to this chart over and over again this winter. For now, all we need to know is this. Starting Pitchers today pitch in a high-homer, high strikeout environment by historical standards, and the magnitude of the differences are huge. The twenties was a high run-scoring environment, but strikeout and homer rates were at about 1/2 of what they are now. This means that Pitchers generally played a much smaller role in run prevention as compared with defence than they do now, and perhaps explains the careers and post-career fame that Rabbit Maranville and Pie Traynor had.
Next, we'll look at measures of quantity- innings pitched, batters faced, across time.